casting is also called cast steel gear.
It is because most of gears are made by
cast steel. Herein, I share
some information about producing gear
casting and related heat treatment.
As for the weights, the
gear castings are normally
from several kilogram to over tons.
As for the materials, gear castings were
usually made by high carbon cast steel,
and some were made by alloy steel with
some Cr, Ni and Mo in order to reach
high tensile strength. Normally large
gears have lower physical requirement
than small gears.
As for the
casting process, usually
molding process is suitable and
enough for the normal requirements. For
cast steel gears, such as bull gear,
pinion and idler, floor molding with
quartz sand will be good choice. Why,
because most of positions of gears need
machining. So, you do not need to use
the higher casting process. In addition,
as for the middle and large steel
castings, floor molding with quartz sand
is almost the only choice.
As for the heat treatment, of course,
the normalization is necessary for all
steel castings in order to erase the
inside stress. Some positions of gear
castings are allowed welding. If the
foundries weld the castings, the anneal
will be necessary for the welding
positions. If the hardness is too high
for gear hobbing, you could do the
anneal again to reduce the hardness and
erase the hard spots inside. After
machining and hobbing, the gears need
quenching or called hardening treatment
to enhance the surface hardness of gear
teeth. For small gears, you could do the
carburizing treatment. For large bull
gears, you could do the surface
quenching treatment. The gears without
hardening treatment have very short
lifetime, from several weeks to several
Since the gear castings have higher
requirements to materials, defects,
machining and heat treatment. Moreover,
the order volume for gear castings are
small relatively. Therefore, many steel
foundries were not willing to make them.
Some gears are made by forging process.
Forging gears have better internal
organization of dense, high strength.
Forged gears could be used in the more
stringent working conditions. Cast gears
have low intensity, but widely used in
the general working conditions. Forged
gears need high costs, and cast gears
need lower costs comparatively. The
buyers should choose the suitable
manufacturing process according to the
cost and conditions of use. In addition,
as for the alloy steel, you should
consider to use the casting process.
The following are some photos of gear
Dandong Foundry made before,
such as small gears, bull gears,
pinions, idlers and large gear.
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